Conceptual issues in quantum cosmology

Abstract

I give a review of the conceptual issues that arise in theories of quantum cosmology. I start by emphasising some features of ordinary quantum theory that also play a crucial role in understanding quantum cosmology. I then give motivations why spacetime cannot be treated classically at the most fundamental level. Two important issues in quantum cosmology -- the problem of time and the role of boundary conditions -- are discussed at some length. Finally, I discuss how classical spacetime can be recovered as an approximate notion. This involves the application of a semiclassical approximation and the process of decoherence. The latter is applied to both global degrees of freedom and primordial fluctuations in an inflationary Universe.

31 pages, LATEX, needs Springer macro cl2emult.cls, 3 eps-figures, contribution for the Karpacz winter school 1999

References in corpus (8)

• Arrow of time in a recollapsing quantum universe
• What is the Geometry of Superspace ?
• Wheeler-DeWitt equation and Feynman diagrams
• Wheeler-Dewitt Metric and the Attractivity of Gravity
• Topology, Decoherence, and Semiclassical Gravity
• Boundary Conditions in Quantum String Cosmology
• Effective action and decoherence by fermions in quantum cosmology
• Quantum state correction of relic gravitons from quantum gravity